Loginova N V, Trotsenko Iu A
Mikrobiologiia. 1977 Mar-Apr;46(2):210-6.
A typical facultative methylotroph Pseudomonas oleovorans oxidizes methanol to formaldehyde by a specific dehydrogenase which is active towards phenazine metosulphate. Direct oxidation of formalydehyde to CO2 via formiate is a minor pathway because the activities of dehydrogenases of formaldehyde and formiate are lwo. Most formaldehyde molecules are involved in the hexulose phosphate cycle, which is confirmed by a high activity of hexulose phosphate synthase. Formaldehyde is oxidized to CO2 in the dissimilation branch of the cycle providing energy for biosynthesis; this confirmed by higher levels of dehydrogenases of glucose-6-phosphate and 6-phosphogluconate during the methylotrophous growth of the cells. The acceptor of formaldehyde (ribulose-5-phosphate) is regenerated and pyruvate is synthesized in the assimilation branch of the hexulose phosphate cycle. Aldolase of 2-keto-3-deoxy-6-phosphogluconate plays an important role in this process. Further metabolism of trioses involves reactions of the tricarboxylic acid cycle which performs mainly an anabolic function due to complete repression of alpha-ketoglutarate dehydrogenase during the methylotrophous growth. The carbon of methanol is partially assimilated as CO2 by the carboxylation of pyruvate or phosphoenolpyruvate. NH+4 is assimilated by the reductive amination of alpha-ketoglutarate.
典型的兼性甲基营养菌食油假单胞菌通过一种对吩嗪硫酸甲酯有活性的特异性脱氢酶将甲醇氧化为甲醛。通过甲酸将甲醛直接氧化为二氧化碳是一条次要途径，因为甲醛和甲酸脱氢酶的活性较低。大多数甲醛分子参与磷酸己酮糖循环，这一点通过磷酸己酮糖合酶的高活性得到证实。甲醛在循环的异化分支中被氧化为二氧化碳，为生物合成提供能量；这一点通过细胞甲基营养生长过程中葡萄糖-6-磷酸和6-磷酸葡萄糖酸脱氢酶的较高水平得到证实。甲醛的受体（5-磷酸核酮糖）得以再生，丙酮酸在磷酸己酮糖循环的同化分支中合成。2-酮-3-脱氧-6-磷酸葡萄糖酸醛缩酶在这一过程中起重要作用。丙糖的进一步代谢涉及三羧酸循环的反应，由于在甲基营养生长过程中α-酮戊二酸脱氢酶完全受到抑制，三羧酸循环主要发挥合成代谢功能。甲醇的碳通过丙酮酸或磷酸烯醇丙酮酸的羧化作用部分以二氧化碳的形式被同化。NH₄⁺通过α-酮戊二酸的还原胺化作用被同化。
